Umm … if you are a total newb with HTML then it’s gonna be a bumpy ride.
I was unaware that you were using an image so the code must change. Also, you are assigning a class of buttons but your class name on the element is button which will not work you must have same class name in your css or change your class name to “buttons”.
transition: background-image 1s ease-out;
or to effect all background you can use
transition: background 1s ease-out;
class name must be the same.